A pocket of very dry air about 2000-3000 feet above the ground helped create conditions just right this morning for a few pockets of mixed rain and sleet/snow across the Florida panhandle. In fact, through much of the night the airport in Tallahassee was reporting occasional rain/snow mix. How did dry air help?
Above, you can see something called a Skew-T diagram from Tallahasee taken at 7 PM last night. The red line is temperature, the green line is moisture in the atmosphere... the closer these two lines are together, the closer the humidity is to 100%. See how far apart the lines are in the lowest levels of the atmosphere? This is bone dry air!
Well, in that 2000-3000 foot layer above the ground, prior to precipitation falling temperatures were above freezing -- which would have lead to all rain. However, initially the precipitation that fell through this layer evaporated because the air was so dry. Evaporation is a cooling process... so as the water drops evaporated, the air cooled down and the humidity approached 100%. This sent this layer of the atmosphere that was once above freezing well below freezing.. helping to produce some wintry precip in the panhandle. In fact, later today was even colder air filters in, the western panhandle could see up to an inch of snow! Even more snow is possible into GA/AL/MS.. where 2-4" could fall and winter storm warnings are up. What a remarkable winter!
